Based on http://search.cpan.org/dist/Module-
Build/lib/Module/Build.pm#distmeta I was led to believe that
Module::Build supported version 2 of the CPAN Meta Spec. I wasted a lot
of time trying different things in my Build.PL before debugging the
Module::Build code and finding out that it is apparently hardcoded at
1.4. Ideally it would support whatever version you pass in via 'meta-
spec' => { version => $version }, but until then, the docs need to be
clearer about which version is supported.